A conventional vehicle internal combustion engine is, as described in Japanese Patent No. 3427452-B2, provided with an intake control valve located in an intake passage of the engine for adjusting a flow of intake air. The opening of the intake control valve is controlled in three stages in accordance with an engine operation condition such as engine rotational speed and/or engine load. As a result, strength of a swirl flow or a tumble flow generated in a cylinder of the engine is adjusted in accordance with an engine operating condition to stabilize the combustion state in the cylinder.
In addition, as shown in Japanese Unexamined Patent Publication No. JP-62-85148A, an internal combustion engine is provided with an in-cylinder pressure sensor located in each cylinder thereof. A combustion period of the engine is calculated based upon an in-cylinder pressure detected by the in-cylinder pressure sensor to determine a swirl ratio correction amount based upon the combustion period, an engine rotational speed and an intake air amount. An opening of the intake control valve (i.e., swirl control valve) is corrected by using the swirl ratio correction amount.
In the technology described in Japanese Patent No. 3427452-B2, however, the opening of the intake control valve is simply switched in accordance with an engine rotational speed and an engine load. Therefore, the strength of the swirl flow or the tumble flow may be reduced due to opening variation of the intake control valve because of dimension variation of the intake control valve, play of a gear in a drive portion thereof, or the like, thus deteriorating the combustion state. Even upon occurrence of such deterioration of the combustion state, it is difficult to correct the combustion state with the conventional technology.
In addition, in the technology described in Japanese Unexamined Patent Publication No. JP-62-85148A, a combustion period is calculated based upon an in-cylinder pressure detected by the in-cylinder pressure sensor and a swirl ratio correction amount based upon the combustion period and an engine operating condition (rotational speed or intake air amount) is used to correct an opening of the intake control valve. That is, the combustion period is used as a parameter for evaluating a combustion state of the engine. On the other hand, a combustion period varies with an engine operating condition (rotational speed or load). Therefore, for correcting an opening of the intake control valve in without influence of the engine operating condition, the correction amount of the opening in the intake control valve is calculated based upon the combustion period and the engine operating condition (rotational speed or intake air amount). This results in complication of calculation processing at the time of correcting the opening of the intake control valve, thereby increasing a calculation load of a controller.
In view of the above, there exists a need for a controller for an internal combustion engine which overcomes the above mentioned problems in the conventional art. The present disclosure addresses this need in the conventional art as well as other needs, which will become apparent to those skilled in the art.